Photoelectrochemical properties of melanin

Melanin is to the animal kingdom like chlorophyll to the vegetal kingdom(1). Melanin collects energy from lower-energy radiation sources, kicks electrons into excited states, initiating a process that would end up producing chemical energy, similar to the way in which photosynthesis supplies energy to plants. However, the precise roles of melanin during this process are unknown. Here we show that the increase in the electron-transfer properties of melanin is independent of the energy of the incident photons. We found in controlled in vivo assays that melanin has the remarkable capability of converting lower-energy radiation towards a more useful form of energy. Furthermore, we found that melanin can break up water molecules and giving up energy suggesting an additional behavior mode for melanin. Our results demonstrate how members of the melanin family are likely to function as transducers, oxidizing water, pushing apart water molecules, as well as recruiting back ions into molecules that are subsequently polarized again. Melanin drives the photon energy of lower-energy radiation sources by quenching electrons and initiating an ionic event independently of their relative energy contention. We anticipate our assay to be a starting point for more sophisticated photoelectrochemical applications. For example, the individual and combined action of multiple photovoltaic applications could be tested, including conducting polymers, for example poly-(phenylenevinylene) (PPV) derivatives or C60 particles. Furthermore, melanin's energy conversion ability is a major target of solar energy conversion development, and an organic-semiconductor way for photoelectrochemical applications will be relevant for such developments.</sup></sup&#x3e

Stable gauged maps

We give an introduction to moduli stacks of gauged maps satisfying a stability conditition introduced by Mundet and Schmitt, and the associated integrals giving rise to gauged Gromov-Witten invariants. We survey various applications to cohomological and K-theoretic Gromov-Witten invariants.Comment: Survey for the 2015 AMS Summer Institute on Algebraic Geometry. Split off from the more technical paper "Properness for scaled gauged maps" [arXiv:1606.01383]. There is still substantial overlap between the two papers. This version has minor correction

RATES OF RETURN TO PRIVATE AGRICULTURAL EXTENSION: EVIDENCE FROM TWO FARM MANAGEMENT CENTERS IN EL SALVADOR

This paper evaluates the economic and the financial viability of implementing private farm management centers (FMC) in El Salvador. In doing so, an ex ante cost-benefit analysis is performed. The results of this analysis suggest that a combination of better farm prices (paid and received), reallocation of resources, and crop diversification that would be promoted by a FMC can lead to an increase in farm level profits that is sufficient to cover the operation of the center and to still generate net gains in household income.Farm Management,

THE EFFECT OF SOIL CONSERVATION ON TECHNICAL EFFICIENCY: EVIDENCE FROM CENTRAL AMERICA

This study evaluates technical efficiency (TE) levels for rural households under high and low levels of investments in soil conservation in El Salvador and Honduras. To correct for potential self-selectivity bias a household-level switching regression framework is implemented to estimate separate stochastic production frontiers for the two groups of households under analysis. The main results indicate that a systematic difference exists between the two studied groups. Specifically, households with higher levels of investments in soil conservation show higher average TE than those with a lower level of investments. Constrains in the rural land and credit markets appear to be the reason behind these differences. Our estimations indicate that for farms with lower levels of investments in soil conservation access to credit is a significant factor explaining the sources of inefficiency. Conversely, households with higher levels of investments in soil conservation present the highest partial output elasticity for land, the highest levels of TE and the smallest farms. This result could suggest the presence of a market failure in the land market which is denying access to land to the more efficient producers.Land Economics/Use,

Optimal Crop-Insurance Strategies under Climate Variability: Contrasting Insurer and Farmer Interests

This study analyzes the potential synergies and conflicts of interest between farmers and insurers in the selection of an optimal crop insurance contract. Special attention is given to how climate information influences this decision-making process. To do so, we consider a representative 40 hectares, rainfed, cotton-peanut farm located in Jackson County in Florida. Our results show that year-to-year ENSO-based climate variability affects farmers income and insurers gains according to crop insurance contracts. Additionally, introduction of ENSO-based climate forecasts presents a significant impact on the selection of a particular contract. We conclude that insurers and farmers can bridge their divergent interests by improving their understanding of the effect of climate conditions on the development of sustainable business plans.Environmental Economics and Policy, Risk and Uncertainty,

Soil conservation and technical efficiency among hillside farmers in Central America: a switching regression model

The main objective of this paper is to evaluate and analyse technical efficiency (TE) levels for hillside farmers under different levels of adoption of soil conservation in El Salvador and Honduras. A switching regression model is implemented to examine potential selectivity bias for high and low level adopters, and separate stochastic production frontiers, corrected for selectivity bias, are estimated for each group. The main results indicate that households with above-average adoption show statistically higher average TE than those with lower adoption. Households with higher adoption have smaller farms and display the highest partial output elasticity for land. Constraints in the land and credit markets are likely explanations for these differences. In addition, all estimated models show that TE has a positive and significant association with education and extension.Central America, soil conservation, stochastic frontiers, switching regression, technical efficiency, Resource /Energy Economics and Policy,

Technical Efficiency and Adoption of Soil Conservation in El Salvador and Honduras

A household-level switching regression model is implemented to examine potential selectivity bias for rural households under high and low levels of investments in soil conservation in El Salvador and Honduras. In the presence of selectivity bias, separate stochastic production frontiers are estimated for low and high adopters. The main results indicate that households with higher levels of investments in soil conservation show higher average TE than those with a lower level of investments. Constrains in the rural land and credit markets are likely explanations for these differences. The results also indicate that for farms with lower levels of investments in soil conservation access to credit is a significant factor explaining the sources of inefficiency. Conversely, households with higher levels of investments have the highest partial output elasticity for land, the highest levels of TE and the smallest farms. These results are consistent with the presence of a failure in the land market which would limit access to land to the more efficient producers.Stochastic Frontiers, Technical Efficiency, Switching Regression, Central America, Soil Conservation, Land Economics/Use, d24, q12, o13, c21,

The Effect of Traditional Practices in the Efficiency of Dairy Farms in Wisconsin

The US dairy sector is facing structural changes including a geographical shift in dairy production and a tendency towards the implementation of more intensive production systems. These changes might significantly affect farm efficiency, profitability and the long-term economic sustainability of the dairy sector, especially in more traditional dairy production areas. Consequently, the goal of this study was to examine the impact of practices commonly used by dairy farmers and the effect of intensification on the performance of the farms. We used a sample of 273 Wisconsin dairy farms to estimate a stochastic production frontier simultaneously with a technical inefficiency model. The empirical analysis showed that at a commercial level the administration of bovine somatotropin hormone to lactating cows increases milk production. In addition, we found that production exhibits constant returns to scale and that farm efficiency is positively related to farm intensification, the level of contribution of family labor in the farm activities, the use of a total mixed ration (TMR) feeding system and the milking frequency.Technical inefficiency, stochastic production frontier, intensification, Livestock Production/Industries, Productivity Analysis,

Analyzing the Determinants of Technical Efficiency Among Traditional Dairy Farms in Wisconsin: A Quantile Regression Approach

This study analyzes the determinants of TE among traditional dairy farms in the State of Wisconsin taking into account dairy farms’ heterogeneity. To do so, we first estimate a production frontier and the level of TE using the SPF framework. Then we analyze the determinants of TI using a quantile regression analysis. The results indicate that the determinants of TE affect in very specific ways farmers with different levels of TE. This result confirms our hypothesis on the importance of controlling for farm heterogeneity when analyzing the determinants of TE. This issue is also important from an empirical point of view. Policy makers could improve the effectiveness of their work by targeting specific agricultural services and aid designed for farmers with different level of TE.technical efficiency, dairy, quantile regression, Agribusiness, Agricultural and Food Policy, Marketing, Production Economics, Productivity Analysis,